Transportable Wastewater Treatment Tank

ABSTRACT

The disclosed embodiments provide a fiberglass (i.e., fiberglass-reinforced polymer) wastewater treatment tank that has at least one lower portion and an upper portion that are joined above the tank water line. The lower portion or portions is/are tapered to allow a plurality of tanks to be nested in a shipping configuration. The top portions may optionally be tapered to allow them to also nest during shipping. Interior tank elements such as clarifier walls, risers, BAT media, aerators, divider walls, piping, etc. can be stacked and shipped within the uppermost of the nested lower portions or possibly used as packing material between nested tanks.

This application claims the benefit of U.S. Provisional Application Ser.No. 61/256,134, filed Oct. 29, 2010, which is hereby incorporated byreference for all purposes.

BACKGROUND

Concrete wastewater treatment tanks, such as those disclosed in U.S.Pat. No. 5,484,524, are currently manufactured through localdistributors. Pre-cast concrete wastewater treatment tanks weighapproximately 10,000 pounds, cost approximately $400-$700 tomanufacture, and can be very expensive to ship to distant installations.Furthermore, in some situations shipping distance or space restrictionsprevent the use of a pre-cast concrete tank, but the soil adjacent aninstallation location is too wet or soft to support the weight of aconcrete delivery truck.

FIGS. 1, 2A-2B and 3A-3B disclose some of the features and dimensions ofprior art systems, like the Jet BAT® J500 Series waste water treatmentplants, that utilize prior art concrete tanks. FIG. 1 discloses a sideview of a prior art single aerator wastewater tank in accordance withU.S. Pat. No. 5,484,524. Influent containing concentrations ofpollutants of various kinds enters the pre-treatment chamber 4 throughan influent line 1. Influent may be from a variety of sources such assewage from an individual house or from a municipality. Large organicand inorganic solids that settle out of the influent and for a timeremain at the bottom of the pre-treatment chamber 4 where they are actedon physically and biochemically. A sludge layer builds up on the bottomof the pre-treatment chamber as organic matter is broken down by theaction of anaerobic bacteria. This action also results in a decrease inorganic particle size which particles subsequently flow to the biofilmaeration chamber. Fluid containing suspended solids (reduced in size)and dissolved organic matter exits the pre-treatment chamber through anout flow 5.

The settled liquid is then flowed into the biofilm-aeration chamber 7from the pre-treatment chamber 4. The biofilm-aeration chambercomprises, in the preferred embodiment, plastic biofilm supportstructure 12 coated with a biofilm (sometimes referred to as “biomass”or “biological agents” herein) and a submerged mechanical aerator. Theliquid is immediately combined with mixed liquor that already isundergoing treatment in the chamber by the swirling action of a hollowaspirator tip 8 which is connected to an electric motor 11 (e.g., 3450RPM) by a hollow shaft 9.

Because of the rotation of an aspirator, a drag force is created at theapertures of the tips and a pressure differential is also produced here.Air is drawn into the hollow aeration tube 9 through the vent cap 22down to the aspirator tip 8 where the air is injected into the mixedliquor as tiny bubbles. Rapid mixing of the tiny bubbles occurs oncethey emerge from the tips of the aspirator 8. High oxygen transfer isaccomplished by this high speed mechanical rotation and air injectionprocess.

The submerged aspirator tip 8 rotates at speeds sufficient to reduce theaverage particle size of the mixed liquor suspended solids (MLSS) intomuch reduced-size particles. It has been found that aspirator arm tipspeeds of 20 ft/sec and higher are effective for performing the particlesize reduction function. The swirling motion created by the aspiratortip together with the lifting motion of the air injected into the mixedliquor circulates the smaller organic particles through the plasticbiofilm support structure 12 on which the biofilm is growing.

Circulation of the mixed liquor is created in the biofilm aerationchamber by the swirling motion of the aspirator tip 8 and by virtue ofair that is injected into the mixed liquor radially from the hollowaspirator tip, which produces the fluid flow.

The amount and physical configuration of biofilm support structurepresent in the process typically comprises a volume of biofilm ofbetween 10% and 99% of the total volume of the biofilm aeration tank andprovides an effective treatment of wastewater with the combination ofother elements of the present invention. It has been found thatapertures in the biofilm of ½″ and larger are satisfactory diameters foruse in such systems.

The mixed liquor passes through the biofilm coated tubes due to fluidflow generated by the rapidly rotating aspirator. The small MLSSparticles and dissolved organic matter are readily adsorbed onto thesurface of the biofilm which is growing on the tube walls. Themicroorganisms of the biofilm are in an oxygen-rich, nutrient-richenvironment, and the organic matter and pollutants are digested by thebiomass. Thus the mixed liquor is purified by this digestive action ofthe biofilm.

Any large particles of organic material that remain undigested by thebiofilm and any old pieces of biofilm which may slough off the interiorof the biofilm tube walls fall into the mixed liquor and again areimmediately reduced in size by the rapidly moving aspirator tips. Theresulting biofilm particles and organic matter are again circulatedthrough the biofilm tubes where biological digestion continues. Theresultant suspended solids from this process is extremely low.

While most of the fluid flow circulates in the biofilm aeration chamber7, as the volume of fluid in the biofilm aeration chamber increases as aresult of continuing influent some of the fluid that has been treatedflows or is displaced through a gap between wall 14 and baffle 15 intothe settling chamber 16. Any settled solids in the settling chamber 16,which might consist of small pieces of biofilm or suspended solids thatare not small enough, are returned to the biofilm aeration chamber 7 bya circulation force created by the circulation current in the biofilmaeration chamber.

Walls 14 and 15 of FIG. 1 are installed in parallel. Wall 14 is createdso that a relatively higher velocity fluid flow constantly moves downthe wall of the biofilm aeration chamber circulating fluid back into thechamber thus “drawing” settled solids from the settling chamber 16 backinto the biofilm aeration chamber 7 for further treatment. While theexact configuration of the walls may vary, any configuration whichallows recirculation of fluid and settled particles in the biofilmaeration chamber for purposes of particle reduction and digestion may beused.

The supernatant in the settling chamber 16 is collected and flows outthrough an effluent pipe 20.

FIGS. 2A and 2B disclose engineering figures for the top view andelevation view of a prior art single aerator wastewater tank formed fromconcrete, with the listed dimensions referencing the inside of the tankin inches as 120″ long, 59″ wide and 69″ tall. FIGS. 3A and 3B discloseengineering figures for the top view and elevation view of a prior artdual aerator wastewater tank formed of concrete, with the listeddimensions referencing the inside of the tank in inches as 120″ long,59″ wide and 69″ tall. These Jet-brand systems using a concrete tank arecurrently certified by the National Sanitary foundation (NSF).

BRIEF SUMMARY

The disclosed embodiments provide a fiberglass (i.e.,fiberglass-reinforced polymer) wastewater treatment tank that has atleast one lower portion and an upper portion that are joined above thetank water line. The lower portion or portions is/are tapered to allow aplurality of tanks to be nested in a shipping configuration. The topportions may optionally be tapered to allow them to also nest duringshipping. Interior tank elements such as clarifier walls, risers, BATmedia, aerators, divider walls, piping, etc. can be stacked and shippedwithin the uppermost of the nested lower portions or possibly used aspacking material between nested tanks to prevent settling.

IEmbodiments disclosed herein have a lighter weight alternative that canbe used to service installations that cannot be reached with a concretetank due to either space restrictions or shipping costs. Variousembodiments are able to be affordably shipped to remote locations, suchas outside of the country.

Additionally, a lighter weight tank that mirrors the inside dimensionsof the concrete waste treatment plants may not require a re-test andrecertification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior art wastewater treatment plant with aconcrete tank;

FIGS. 2A and 2B illustrate a prior art single aerator wastewatertreatment plant with a concrete tank;

FIGS. 3A and 3B illustrate a prior art dual aerator wastewater treatmentplant with a concrete tank;

FIGS. 4A and 4B illustrate a first embodiment of a fiberglass wastewatertreatment tank;

FIG. 4C illustrates interlocking wall details of a first embodiment of afiberglass wastewater treatment tank;

FIGS. 5A and 5B illustrate a second embodiment of a fiberglasswastewater treatment tank;

FIGS. 5C and 5D illustrate interlocking wall details of a secondembodiment of a fiberglass wastewater treatment tank;

FIGS. 6A and 6B illustrate a third embodiment of a fiberglass wastewatertreatment tank;

FIG. 6C illustrates interlocking wall details of a third embodiment of afiberglass wastewater treatment tank; and

FIG. 7 illustrates a nested arrangement of fiberglass wastewatertreatment tanks.

DETAILED DESCRIPTION

In order to provide a fiberglass (i.e., fiberglass-reinforced polymer)wastewater treatment tank/plant that matches currently-certifiedtanks/plants, there are several design considerations that should betaken into account. Current plants hold approximately 1,250 gallons ofwater and anything that can be flushed down a toilet will end up in thistank, so the tank must be capable of resisting normal householdchemicals and waste at least as well as concrete. The tank must also becapable of being buried 3-5 feet below the ground. As such, the polymerselected should be resistant to household chemicals and have sufficientthickness and reinforcing fiberglass to withstand the expected loading.

Such tanks will be periodically pumped out as part of the normalmaintenance. This means that there should be some method of securing thetank so that it does not float when it is pumped out. When the tank ispumped, one side of the tank or the other will be fully pumped outbefore the other side is. This means that the wall between the twocompartments (pre-treatment and aerator or plural aerator compartments)must be capable of holding back the weight of the water from the othertank. The tank must also support the 30 pound aerator, typically via ariser. Embodiments must also provide access ports as found in certifiedsystems (as depicted in FIGS. 1, 2A-2B and 3A-3B) in order to allowtechnicians to clear any obstructions, pump out the tank, and servicethe media. In order to comply with presently-existing rules, thereshould not be any seams below the water line of the treatment tank.

Preferably, the tanks should be able to nest to reduce shipping costs.One way to allow the tanks to nest is to taper at least some of the sidewalls of the tank sections. Because the tanks will be installedunderground, the structure must be strong enough to resist the groundpressures created by the below ground installation. The installed tankmust also be water-tight when installed. In order to allow the tanks tobe used in both single aerator and dual aerator configurations,preferably both the pretreatment and treatment compartments of the plantshould be configured with the necessary supports to hold media and anaerator. The media supports should be sufficiently strong to hold heavymedia containing wet biomass when the compartment has been pumped out.Because the present embodiments will be competing with concrete tanksand competitive fiberglass and roto-molded systems, cost and weight areimportant.

A first embodiment, in which a wall between the pretreatment chamber andthe treatment chamber is “cast” into the lower portion of the tank 100,is disclosed in FIGS. 4A and 4B. These figures are for illustration onlyand the dimensions and amount of tapering are not to scale. Asillustrated in elevation view FIG. 4A, a pretreatment chamber 4 isformed from tapered walls 40, 41 on a one side of a lower portion 110 ofthe tank 100 and the treatment chamber 7 and settling chamber 16 areformed on the other side of the lower portion 110 of the tank 100. A lidportion 112 covers the lower portion 110 of the tank 100 and can beformed as a single portion or as two discrete portions. The lid portion112 joins the lower portion 110 above the waterline of the wastewatertreatment plant so that no seams are below the waterline. The lid 112 ispreferably reinforced to help stabilize the two chambers of the lowerportion 110 and to resist the loading from dirt covering the buriedtreatment plant.

The lids 112 in the first embodiment can be stackable or nestable (usingtapered walls) and the lower portion 110 has tapered walls so as to benestable for storage and shipping. The lid 112, hanging baffle 14between the treatment chamber 7 and settling chamber 16, and mediasupports 12 a and 15 have interlocking channels 50, 50′ to facilitatelocation and installation of the clarifier wall 14 and media aftershipping to the final destination. As shown in the top view of FIG. 4Band the detail of FIG. 4C, the interlocking channel configuration canimprove the structural rigidity and integrity of the plant. While notillustrated, the plant will have risers for installation of aerators andmaintenance access to the various chambers of the plant. The risers canbe lightweight and formed of suitable material such as plastic orfiberglass. In certain embodiments, the risers can be tapered tofacilitate nested storage and shipping.

A second embodiment, in which a wall 60 between the pretreatment chamber4 and the treatment chamber 7 is field-installed into the lower portion110 of the tank 100, is disclosed in FIGS. 5A and 5B. These figures arefor illustration only and the dimensions and amount of tapering are notto scale. As illustrated in elevation view FIG. 5A, a pretreatmentchamber 4 is formed on a one side of a lower portion 110 of the tank 100by the installation on-site of a divider wall 60. The bottom wall 30 ofthe lower portion 110 of the tank 100 includes raised portions 35, 35′to assist in sealing the divider wall 60. The remainder of the tankforms the treatment chamber 7 and settling chamber 16 on the other sideof the lower portion 110 of the tank 100. A lid portion 112 covers thelower portion 110 of the tank 100 and is formed as a single portion. Thelid portion 112 joins the lower portion 110 above the waterline of thewastewater treatment plant so that no seams are below the waterline. Thelid 112 can preferably be reinforced to help resist the loading fromdirt covering the buried treatment plant.

The lids 112 in the second embodiment can be stackable or nestable(using tapered walls) and the lower portion 110 has tapered walls so asto be nestable for storage and shipping. The lid 112, divider wall 60,hanging baffle 14 between the treatment chamber 7 and settling chamber16, and media supports 15 and 12 a have interlocking channels 50, 50′ tofacilitate location and installation of the divider wall 60, theclarifier wall 14 and media after shipping to the final destination. Asshown in the top view of FIG. 5B and the detail of FIGS. 5C-D, theinterlocking channel configuration can improve the structural rigidityand integrity of the plant. While not illustrated, the plant will haverisers for installation of aerators and maintenance access to thevarious chambers of the plant. The risers can be lightweight and formedof suitable material such as plastic or fiberglass. In certainembodiments, the risers can be tapered to facilitate nested storage andshipping.

A third embodiment, in which the pretreatment chamber 4 and thetreatment chamber 7 are formed by separate lower tank portions, isdisclosed in FIGS. 6A and 6B. These figures are for illustration onlyand the dimensions and amount of tapering are not to scale. Asillustrated in elevation view FIG. 6A, a separate pretreatment chamber 4is formed from a tank 106 with tapered walls 40 on a one side of a lowerportion of the plant. The treatment chamber 7 and settling chamber 16are formed with a separate tank 108 on the other side of the lowerportion of the plant. A lid portion 112 covers the two lower tanks 106,108 and can be formed as a single portion or as two discrete portions.The lid portion 112 joins the lower portion tanks 106, 108 above thewaterline of the wastewater treatment plant so that no seams are belowthe waterline. The lid 112 is preferably reinforced to help stabilizethe two tank chambers of the lower portion and to resist the loadingfrom dirt covering the buried treatment plant.

The lids 112 in the third embodiment can be stackable or nestable (usingtapered walls) and the lower portions have tapered walls so as to benestable for storage and shipping. The lid 112, hanging baffle 14between the treatment chamber 7 and settling chamber 16, and mediasupports 15, 12 a have interlocking channels 50, 50′ to facilitatelocation and installation of the clarifier wall 14 and media aftershipping to the final destination. As shown in the top view of FIG. 6Band the detail of FIG. 6C, the interlocking channel configuration canimprove the structural rigidity and integrity of the plant. While notillustrated, the plant will have risers for installation of aerators andmaintenance access to the various chambers of the plant. The risers canbe lightweight and formed of suitable material such as plastic orfiberglass. In certain embodiments, the risers can be tapered tofacilitate nested storage and shipping.

In another (non-illustrated) embodiment, the risers can be tapered andformed integral with tapered lids so as to nest within one another.

FIG. 7 illustrates a nested arrangement of fiberglass wastewatertreatment tanks 101. Again, this figure is for illustration only and thedimensions and amount of tapering are not to scale. Also, althoughdisclosed in accordance with the first embodiment, the other embodimentscan equally be stored and shipped in such a nested manner. By taperingat least some of the sidewalls of the lower portions 110 of the plant,the lower portions 110 can be stored and shipped in a nested manner. Asillustrated in FIG. 7, a plurality of lower portions 110 are stacked ontop of each other in a nested manner with packing material 18therebetween to control the level of settling.

Baffle walls 14, divider walls (not illustrated), and media supports 17for the plurality of plants can be stacked and stored inside theuppermost nested tank portion. These components, as well as BAT media,piping, risers, aerators, electrical controls, etc. can also be storedand shipped inside the uppermost tank. The plurality of lids 112 can benested or stacked on top of the nested lower portions 110 for storageand shipping. If suitably designed, the packing material 18 can beformed of components, such as risers and supports, so as to allowadditional space for plant components and the like in the uppermosttank.

While it is preferable that the wastewater treatment plant maintain thedimensions of certified plants, it is also possible to use otherdimensions. In order to provide light weight and strength, thefiberglass-reinforced polymer walls of the treatment plant can be formedwith corrugations, ribs, webs, and other such structures as generallydisclosed in co-pending U.S. application Ser. No. 11/949,900 so as toincrease the strength of the walls, which is hereby incorporated byreference. (Note: do we want to claim priority to this application??)

IN view of the above, in a basic embodiment, a tank for a wastewatertreatment plant, comprises at least one lower tank portion having abottom wall and side walls, wherein at least some of the side walls aretapered so as to allow identical lower tank portions to nest therein,wherein the side walls extend above a waterline of the treatment plant,and at least one lid portion for joining to the at least one lowerportion, wherein the at least one lower portion and the at least one lidportion are formed from fiberglass-reinforced polymer. A first variationof this embodiment comprises a single lower tank portion with a taperedpair of walls forming a divider wall between a pretreatment chamber anda treatment chamber. Preferably, the first embodiment comprises a singlelid portion, wherein the single lid portion preferably comprises areinforcement spanning the divider wall in the single lower portion.

In another embodiment, the tank for the wastewater treatment plantcomprises one lower tank portion and a separate divider wall for on-siteinstallation between a pretreatment chamber and a treatment chamber.This second embodiment may further comprise raised portions in thebottom wall for assisting in sealing the divider wall. Preferably, thissecond embodiment comprises a single lid portion, wherein the single lidportion preferably comprises a reinforcement spanning the divider wallin the single lower portion.

In yet another embodiment, the tank for the wastewater treatment plantcomprises two lower tank portions with a first lower tank portionforming a pretreatment chamber and second lower tank portion forming atreatment chamber and a settling chamber. Preferably, this thirdembodiment comprises a single lid portion, wherein the single lidportion preferably comprises a reinforcement spanning the first lowertank portion and the second lower tank portion.

Preferably, all of the embodiments further comprise media supportsformed in at least the treatment chamber and preferably in both thepretreatment chamber and the treatment chamber.

A system and method for providing a lightweight, transportablewastewater treatment plant has been described. It will be understood bythose skilled in the art that the present invention may be embodied inother specific forms without departing from the scope of the inventiondisclosed and that the examples and embodiments described herein are inall respects illustrative and not restrictive. Those skilled in the artof the present invention will recognize that other embodiments using theconcepts described herein are also possible. Further, any reference toclaim elements in the singular, for example, using the articles “a,”“an,” or “the” is not to be construed as limiting the element to thesingular.

1. A tank for a wastewater treatment plant, comprising: at least onelower tank portion having a bottom wall and side walls, wherein at leastsome of the side walls are tapered so as to allow identical lower tankportions to nest therein, wherein the side walls extend above awaterline of the treatment plant; and at least one lid portion forjoining to the at least one lower portion; wherein the at least onelower portion and the at least one lid portion are formed fromfiberglass-reinforced polymer.
 2. The tank for a wastewater treatmentplant of claim 1, comprising a single lower tank portion with a taperedpair of walls forming a divider wall between a pretreatment chamber anda treatment chamber.
 3. The tank for a wastewater treatment plant ofclaim 2, comprising a single lid portion.
 4. The tank for a wastewatertreatment plant of claim 3, wherein the single lid portion furthercomprises a reinforcement spanning the divider wall in the single lowerportion.
 5. The tank for a wastewater treatment plant of claim 3,further comprising media supports in at least the treatment chamber. 6.The tank for a wastewater treatment plant of claim 5, further comprisingmedia supports in the pretreatment chamber.
 7. The tank for a wastewatertreatment plant of claim 1, comprising one lower tank portion and aseparate divider wall for on-site installation between a pretreatmentchamber and a treatment chamber.
 8. The tank for a wastewater treatmentplant of claim 7, further comprising raised portions in the bottom wallfor assisting in sealing the divider wall.
 9. The tank for a wastewatertreatment plant of claim 7, comprising a single lid portion.
 10. Thetank for a wastewater treatment plant of claim 9, wherein the single lidportion further comprises a reinforcement spanning the divider wall inthe single lower portion.
 11. The tank for a wastewater treatment plantof claim 7, further comprising media supports in at least the treatmentchamber.
 12. The tank for a wastewater treatment plant of claim 11,further comprising media supports in the pretreatment chamber.
 13. Thetank for a wastewater treatment plant of claim 1, comprising two lowertank portions with a first lower tank portion forming a pretreatmentchamber and second lower tank portion forming a treatment chamber and asettling chamber.
 14. The tank for a wastewater treatment plant of claim13, further comprising media supports in at least the treatment chamber.15. The tank for a wastewater treatment plant of claim 13, comprising asingle lid portion.
 16. The tank for a wastewater treatment plant ofclaim 15, wherein the single lid portion further comprises areinforcement spanning the first lower tank portion and the second lowertank portion.
 17. The tank for a wastewater treatment plant of claim 14,further comprising media supports in the pretreatment chamber.
 18. Thetank for a wastewater treatment plant of claim 5, wherein the mediasupports comprise interlocking channels.
 19. The tank for a wastewatertreatment plant of claim 11, wherein the media supports compriseinterlocking channels.
 20. The tank for a wastewater treatment plant ofclaim 14, wherein the media supports comprise interlocking channels.